The invention relates to aircraft warning systems and more particularly to warning systems that provide warnings of various types of flight hazards such as wind shear and potential collisions with the ground or other aircraft.
Over the last twenty years a number of sophisticated flight hazard warning systems have been developed for aircraft which have contributed substantially to flight safety. These systems include ground proximity warning systems for providing warnings of controlled flight into terrain type accidents, traffic alert and collision avoidance systems and wind shear detection systems.
However, because in most cases these systems operate independently of each other, it is possible under some circumstances to get warnings from more than one system at about the same time. Further, these warnings can conflict. For example, there are situations in which a ground proximity warning system would generate an aural "Pull Up" warning followed directly by the traffic alert and collision avoidance system generating a "Descend" warning. This type of situation can make it very difficult for the cockpit crew to make a timely determination of the correct response, especially considering the limited time to respond to a given warning.
In one approach to overcoming this problem the flight hazard warning systems generate both an inhibit signal and a warning alert signal. The inhibit signal suppresses alert signals from other warning devices. As an example, a ground proximity warning system can be programmed to generate an inhibit signal which is then transmitted to one or more of the other flight hazard warning systems such as a traffic alert and collision avoidance system.
With the aforementioned approach, every ground proximity warning alert signal will inhibit all traffic alert signals. However, there are situations when it would be advisable to suppress a ground proximity system warning, particularly a Mode 1 warning, in favor of a traffic collision and alert system warning. Similarly, there are some circumstances when a ground proximity Mode 1 warning should take precedence over a predictive windshear warning and other circumstances when the opposite is true. Thus, this approach where one or more flight hazard warning systems is universally programmed to generate inhibit signals for the other systems is overly simplistic and can lead to less than optimal response to a flight hazard on the part of the cockpit crew. Moreover, since there are a very large number of potential flight hazard conditions each with varying criticality and associated probability of an accident occurring, such a simplistic approach is inherently unable to provide optimal warnings of flight hazards.
Another disadvantage of current flight hazard warning systems results from the fact that many aircraft, and in particular commercial aircraft, are equipped with several physically separate systems such as a ground proximity warning system, a traffic alert and collision avoidance system, a reactive windshear system and a predictive windshear system. This federated approach to providing an aircraft with a flight hazard warning system, in addition to the costs of separate hardware, wiring and displays, can make it very difficult to integrate the operations of the systems so as to provide a system where the warnings can be prioritized. In some avionics suites the warning prioritization and interrupts must be implemented using a direct hard wire connection between the systems. Not only is this architecture costly to implement, but this arrangement allows for only a limited prioritization scheme between hazard alerts. In other avionic architectures, the various flight warning systems are connected to a data bus such as the ARINC 429 or 629 buses which transmits the inhibit signals between the systems in lieu of the hardwire connection. This approach still requires that the individual systems each be programmed to transmit the inhibit signals to the specific addresses of the other systems and/or be programmed to receive and to respond to inhibit signals from other systems.
Limited exceptions to the aforementioned architectures are found on some Airbus and Douglas aircraft. On newer generation Airbus and Douglas aircraft, there is no primary reactive windshear detection system. Recovery maneuvers and protection against windshear events are implemented as a part of the flight control system. Prioritization of certain limited hazard alerts such as the windshear alert and altitude call-outs along with other aircraft system failure alerts are performed by a warning unit. However, the major and potentially conflicting alert functions such as GPWS, TCAS, and PrWS are still implemented as federated systems.